There are so many kinds of air purification systems, and so many different reasons for using them, that it is nearly impossible to choose!
The EPA publishes a large amount of guidance on the various types, their effectiveness and precautions. You can begin reading here: https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home
There is more information here: https://www.epa.gov/sites/default/files/2019-09/documents/harriman_stephens_brennan_-_new_guidance_for_residential_air_cleaners_-_ashrae_journal_sept-2019._web_version.pdf

We actually run HEPA air cleaners independent of our furnace/AC system. Otherwise, the whole-house fan must be running all the time, or the air cleaner is doing no good.
If you are seriously thinking of an ozone-producing unit, keep in mind that even small amounts of ozone can increase symptoms of asthma, COPD and other lung disorders. I am not sure what Aprilaire means about safely using ozone.
Sue